There are a variety of potential measures that can be used to evaluate clinic success rates of assisted reproductive technology (ART), and the range of measures can be overwhelming. For example, the success rate in in-vitro fertilization (IVF) is typically presented in one of the following ways.

It can be expressed as a percentage of all treatment cycles started during a given time period that end in pregnancy. This is often referred to as the pregnancy rate per cycle started.

It can be defined as the percentage of embryo transfers that result in pregnancy. This is often referred to as the pregnancy rate per embryo transfer. Pregnancy rate per cycle started will always be lower than the pregnancy rates per embryo transfer. This is because cycles cancelled before embryo transfer are not counted when calculating the pregnancy rate per embryo transfer.

Live birth rate is different from the pregnancy rate, in that approximately 15% of pregnancies achieved through ART will end in miscarriage. The live birth rate, then, is really the number of live births per cycle started.

This may seem confusing, so there is an example below to help you better understand. In this example, there are 100 cycles started, 90 cycles reach the embryo transfer stage, 40 result in pregnancies and 6 of those end in miscarriage.

The pregnancy rate per cycle started then is 40% (40 pregnancies in 100 cycles).

The pregnancy rate per embryo transfer is 44% (40 pregnancies out of 90 embryo transfers).

The live birth rate per cycle started is 34% (100 cycles, with 40 pregnancies, 6 miscarriages, and 34 successful births).

According to the Canadian Fertility and Andrology Society, the 2010 and 2011 Canadian data is as follows:

The average pregnancy rate per cycle started is 32%.

The overall live birth rate per cycle started is 30%.

There was significant variation in these rates according to age, with women under 35 having the highest average pregnancy rates and overall live birth rates.